HVAC filters are often considered to be a low price consumable in the HVAC operation. However, looking more in-depth at the costs may be eye-opening. Air filters perform two main functions: improving indoor air quality and protecting the air handling units. While the prior is often measured in MERV ratings, the latter is mostly determined by observation. Proper filter installation and maintenance are crucial to keeping HVAC coils and ductwork clean. If dirt accumulates in the ductwork, and if the relative humidity reaches the dew point so that condensation occurs, then the ductwork can become a breeding ground for bacteria and mould.
Reduced filtration efficiencies may allow harmful particles to enter the breathing air. Lung-damaging dust can be as small as 0.5 microns, making high filtration efficiencies critical to providing safe and healthy indoor air. In fact, gaps in and around filter banks and heavy soil and debris upstream of poorly maintained filters have been implicated in healthcare-associated outbreaks of infectious diseases.
The customer’s situation
A commercial building owner in the Toronto region evaluated the price of two filter types. The current filters being used were a throw-away cardboard type with a MERV 8 rating. They were using 240 filters per quarterly change out and 80 of them were 30 inch wide custom filters. The typical purchase order for the quarterly change out was $1,150 and the weighted average filter price was $4.80. The customer has 8 buildings of this scale in the region.
Steps in the Life-Cycle
The first step was for vendors to bid on the supply for one building and based on the value of the proposals, a vendor would be selected for a pilot change-out cycle. The Delta M proposal was for a new filter technology that is 100% reusable and recyclable with a return rebate for each dirty filter sent back. The price of the purECOgreen™ filter was $6.49 each. On the surface it appears that the price for filters would increase by almost 26%. However, upon closer examination of the life-cycle cost it became clear that not all costs were apparent. The client found that the investigation led them to savings that were not available under the old filter technology and had not even been considered as a possibility. Here is the comparison they went through:
| Delta M purECOgreen™ pleated filters | Current throw-away pleated filters | |
| Price per filter: |
$6.49 |
$4.80 |
| Case quantity price |
$5.99 |
– |
| Return Rebate per filter |
$1.00 each |
– |
| Volume discount (>500 filters per year) |
$0.35 each |
– |
| Discounted filter price: |
$4.64 |
$4.80 |
In addition, since using the purECOgreen™ filter meant that there would no longer be any need to throw filters into the waste dumpster, they calculated that they would reduce the need for 1 x 20 yard bin per building each year since the bins normally hold about 1,000-1,200 throw-away filters. Each 20 yard bin cost them about $350 under their contract. With those savings divided out over the filter count, the true distributed price of a purECOgreen™ filter was $4.27 and the quarterly building change-out costs were $1,026 or 12% less than the current costs.
Dirt Particles Get in the Way
They also discovered the added value provided by the Sure-Seal gasket on the purECOgreen™ filters. This gasket minimizes all bypass air from contaminating the indoor air quality or foiling the coils and ductwork and forces the air to be filtered at the required MERV rating. Although the customer had taken precautions and fitted all AHU tracks with a foam gasket, there was no way to assure a complete seal of each filter to the adjacent filter in a wide multi filter track. Their research in ASHRAE’s library of research articles found that any gap that forms around a filter will reduce its straining efficiency incrementally over the maintenance cycle. After 3 months the dust loading would deform the cardboard filter so much as to open up a pencil width space between filters and the coils would foul up with unfiltered air.
They took a measurement of the Watts at high operation during each of 4 summer months and found that even a light fouling had an impact on the energy use of the unit. They calculated the increase in kW used each month and annualized it:
| Quantity | Volts | Amps | Watts | kW | Annual Cost | Fouling | 10¢ per kWh | 15¢ per kWh | |
| 10 Ton AHU | 480 | 80 | 66432 | 66.4 | $7,168.00 | 0% (clean coils) | _ | _ | |
| 10 Ton AHU | 480 | 84 | 69753 | 69.6 | $7,516.00 | 5% | $348.00 | $522.00 | |
| 10 Ton AHU | 480 | 88 | 73072 | 72.8 | $7,860.00 | 10% | $692.00 | $1,038.00 | |
| 10 Ton AHU | 480 | 92 | 76396 | 76.4 | $8,248.00 | 15% | $1,080.00 | $1,620.00 |
Not only does the cost of energy consumption go up with fouling of the coils, but the contaminated air enters the ductwork and ends up in the breathing air of the tenants in the building. The gap between the filters that fouled the coils is now also reducing the MERV rating of the air supply system. The gap of 0.2 inches reduced the filter effectiveness by 2 MERV ratings resulting in the building air only straining particle sizes at MERV 6. The cost of a MERV 6 filter is significantly less than the MERV 8 filter price they were paying. Again, the price of the original filter was only one component in the life-cycle cost of air filtration.
The Net Result
When evaluating the price of HVAC filtration it is clear that the costs are distributed over many departmental budgets. The true costs remain hidden if the waste disposal budgets aren’t reduced by the waste diversion savings, the operations budget will be impacted positively by reduced energy costs, and lastly, the labour time of coil and duct cleaning is reduced by 50% meaning that the cleaning can be scheduled once per year instead of semi-annually. Although no dollars were saved on salaries, other more vital building maintenance could be done more timely.
The client selected purECOgreen™ HVAC filters for the pilot and expansion is planned for all buildings.
